Technical Rusty floor pan solutions?

The front floorpans of my '56 Olds project are the victim of sitting with water/mud in them long enough that they have rotted through in the foot pan in front of the seat and riddled with pinholes in the footboards and bottom of the firewall.

The flat floorpans where the biggest problems are, are getting replaced with new sheetmetal, as that area is relatively flat, and I actually found replacement pans made to fit pretty close to the factory profile.

My problem is all the little pinholes in the curved areas of the toeboard and firewall. The compound curves are beyond the scope of my metal working equipment and/or ability I'm afraid, so cutting and patching isn't my favorite solution.

What are my other options? Leading? Fiberglass? I learned the very basics of leading in Windfield's classes, and laying down fiberglass is pretty straight forward, but I'm not sure how well either/both will hold up and are these good options for an area like this with heat and water around it a lot. No matter what I fix it with, I do plan on coating the metal with Lizard Skin or something of that nature to seal and sound deaden it.

 

Good time to learn to form metal by hand.

 

May be use 55-57 Chevy repop panels as a source of curved material,and cut as needed to patch original areas.

 

Good time to make your own floor pans. Cut this out and weld yours in.

 

Cutting it out and replacing the pin hole rusted sheet metal with new metal is the only long term fix. You won't be able to weld to the metal with the pinholes in it anyway, you will just burn through it. 20 gauge sheet metal forms pretty easy, get some extra 20 gauge and add what you need to get past the pin hole section (cut the pin hole crap out) and weld it to your new floor section and to the good metal left in your original floor. Anything short of this means you will be back in there in a couple years and replacing it then, and you might end uplacing some of the new metal your putting in now.

If you really can't weld in the extra sheet metal, fiberglass over the pinhole rusty section is your next best option, and its not a real good one. Be sure that whatever you do there, you cover as much of the old pinholes metal as possible, and make sure the surface you are bonding to is as clean and shinny as possible.

I've done this stuff professionally for over 25 years, metal with pinholes in it is just short of being gone. Rust is cancer to your car, cut it all out and replace the metal with new stuff, or the rust just keeps eating away metal, and you get to do it again in a couple years. Gene

 

These are nothing like the Olds pans. I have done 2 x 56 Olds, you will have to fold up and suage your own panels to get them looking original.

 

Yep, time to learn some metal work. Those pinholes and pittings arent getting any better, if you are going to coat them with something.

 

Make patterns that split the curves, cut and fit gently with 1/2 the shape in each piece and weld them up. You’ll be cutting irregular shaped pieces and then arranging them to straight lines. The 1/2 bends and minor shrinks will be very easy. The trade off is more welding. Think and work as if you were going to cover it with wallpaper for patterns.

Wheel barrows also have some nice floor pan type curves

 

a beer carton is the same thickness as 20 ga make your pattern from it then lay it flat on the metal and trace it . I have used por 15 and fiberglass mat to fix pin holes in floor just paint the por on then lay the mat and put more por on it until it is well coated. if you can put the por on both sides it will last several yrs

 

If you can't weld that area, better than laying fiberglass over top is to grind above and below that weak spot to get to solid metal. Then get some scrap metal and form a patch over that area...use a ball peen hammer to get as close to the shape as you can.clean the mating surfaces ....use panel bond adhesive from 3 M or Lords and some sheet metal screws to hold the patch to the floorboard while the adhesive sets up. This is how they attach the roof section to Chrysler minivans. When the panel is set 4 hrs or overnight ,grind off the screw heads,or leave the screw heads but you might feel them through the carpet. . Undercoat the underside facing the roadway. That floor will be as strong as it ever was.

Then one day in the future you can go back and get the floors redone if you have an extra $2000 -$3000 in your pocket.

 

Replacing the damage with new steel is the best but if you absolutely can't right now, you can coat with POR 15 and then fill pinholes with epoxy just as the POR15 is curing, I have done this but my area was smaller than what is in your photo, I also cleaned down to bare metal and used ospho on the rust first. Do both sides. Not an Ideal repair but some times you have limited options. Holding up OK on my floor.

 

If you don't like rust, you will need to take special care refinishing it after the new metal is welded in. It will need to be sandblasted to remove all the rust from any original steel first. Just grinding or wire brushing will let rust remain down in the pits. That rust will come back.

I'm not a believer in "rust converter" chemicals. Rust will always find moisture and come alive again. You need to remove all the rust.

Which also leads to the point of never make overlapping patch joints. Any place there is an overlap is inviting moisture to sit in between the layers and rust. Seam sealer might work, but can you guarantee every single millimeter of the joint is sealed? A butt weld will remove all worry about this.

Then, after all rust is gone, use a metal prep acid wipe to clean all dirt and residual oils from the steel, and prime with a good epoxy. Spray can primer is not good. Then top coat with a finish paint, even if you plan to use a sound deadener or undercoat over it. You want to seal that primer from any moisture.